Article History
Received: 10 September 2021
Accepted: 11 February 2022
First Online: 23 February 2022
Declarations
:
: This study has been approved by the review board of the Kofu Neurosurgical Hospital to which our institution belongs (approval date: September 16, 2020). Due to the retrospective study design and the use of anonymized patient data, the need for consent to participate was waived by the ethics committee that approved our study. All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
: Not applicable.
: The authors declare that they have no competing interests.